1. Technical Field
The present invention relates to a linear vibration motor.
2. Description of the Related Art
Generally, vibration motors convert electric energy into mechanical energy using the principle of generation of electromagnetic force. Such vibration motors are installed in electronic devices, such as mobile communication terminals, portable terminals, etc., and are used to indicate signal reception in a mute mode.
Furthermore, in accordance with the rapid growth of wireless communication and mobile phone markets, a variety of multifunctional mobile communication terminals have recently gained popularity. This trend requires high quality compact mobile communication terminals. To satisfy such requirements, techniques to improve the performance and quality of vibration motors have been developed.
Moreover, for several years, the number of cellular phones employing large screen LCDs and touch screens has increased rapidly. As a result, there has been increased demand for vibration motors that generate vibration when a user touches an LCD.
Particularly, vibration motors generating vibrations when touch screens are touched require the following characteristics. First, because the number of generation of vibrations is increased compared to that when incoming calls are received, the operational lifespan thereof must be increased. Second, response speed must be enhanced so that a user can feel vibrations in a timely manner when touching the screen.
Linear vibration motors are representative examples of vibration motors which can satisfy the above characteristics. Such linear vibration motors have a resonant frequency determined by a spring and a vibrator coupled to the spring and are vibrated by exciting force generated by electromagnetic force. The electromagnetic force is generated by interaction between a magnet of the vibrator and electric currents which are applied to a coil of a stator and have a predetermined frequency.
In conventional linear vibration motors having the above-mentioned construction, the vibrator collides with a casing or a bracket when it vibrates, thus generating contact noise. In an effort to overcome this problem, a damper (made of rubber, Poron, etc.) or an MF applied in an annular shape on a corresponding surface have been used.
However, in the case of the MF, when excessive force is applied thereto, it may be dispersed and displaced from the correct position, because it is liquid. Thus, the damping performance is deteriorated, resulting in generation of noise when the motor vibrates. Furthermore, damper made of made of rubber, Poron, etc. requires significant space so it is difficult to use in a limited space. Thus, the degree of freedom in motor design is reduced.